There is known issue with some archiver programs like winrar or standard windows integrated archiver.
We always testing with http://www.7-zip.org so please use it for extract and everything should be fine
Or via cpanel/plesk file manager, complete process is described here:
For cpanel: http://iwinter.com.hr/support/?p=4833
For plesk: http://iwinter.com.hr/support/?p=6991